Urgent custom balance request

A quick learner says:
Looks like S770

Goose neck clip.
length of 40"
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Tom from SWISCO responded:

Thanks for reaching out to us. Unfortunately, it's not possible for me to verify whether you have the Series 770 or not based on the provided information. It's important to keep in mind that the stamp isn't a part number or identification code of any kind, all it tells me is how strong the spring is; even then, your stamp is outdated and doesn't match any of our modern options exactly, so at the end of the day it can only allow me to make an educated guess at the weight. I also don't know what a goose neck clip is, or whether it's different from the terminal clip that the Series 770 comes with.

We would need clear photos of the balance in order to verify whether or not the Series 770 is the right assembly; specifically of the top and bottom ends and the metal clip at the end of the cord. If you also wanted to verify the modern version of your 3940 weight rating, I would additionally need the weight of the sash.

If you're not able to get that information and just want to buy this balance as soon as possible, then my best guess is the S770-40 with a 40D stamp option, for sashes weighing 27 through 32 pounds. However I have to stress that this is just a guess. 

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